JPS6039114B2 - Method for producing intermediate Btu gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the gasification of coal and similar carbonaceous materials;
In particular, it relates to a method for producing intermediate B-mount gas by performing a catalytic gasification step in the presence of a carbon-alkali metal catalyst.

Existing processes proposed to date for producing syngas fuel from coal or similar carbonaceous materials or substances generally combine carbon and steam (alone or in combination with oxygen) in a range of about 12,000F-25,000F (649 -137
1° C.), thus producing a gas consisting mainly of hydrogen and carbon monoxide, with some methane.

This gas can be used as synthesis gas or fuel with little additional processing, or it can be directed to a catalytic methanator where it is reacted with additional steam to increase the hydrogen to carbon ratio and convert it to carbon monoxide. It can be used to produce methane by reaction with hydrogen. It has been found that this type of process can be improved by carrying out the first gasification step in the presence of a catalyst containing an alkali metal component. The alkali metal component promotes the steam-carbon gasification reaction so that synthesis gas can be generated at slightly lower temperatures than would be required in its absence. However, this type of reaction process is expensive because a large amount of heat must be supplied to maintain the highly endothermic steam-carbon reaction. One method of providing this heat is to inject oxygen directly into the gasifier to burn off some of the carbon in the feed to be gasified. This method is very expensive as it requires the provision of an oxygen production plant. Other methods of supplying heat have been proposed, but they are as expensive as oxygen injection. Recently, a process has been proposed which circumvents the difficulties associated with processes of the type described above by reacting steam and carbon in the presence of a carbon-alkali metal catalyst and substantially equilibrium amounts of hydrogen and carbon monoxide. Ta.

Laboratory studies and pilot plant tests have shown that catalysts produced by the reaction of carbon with alkali IJ metal compounds such as potassium carbonate form carbon-alkali metal compounds or complexes and, under appropriate reaction conditions, can be used during gasification. It has been shown to equilibrate the gas phase reactions occurring in the gas phase to produce additional methane while simultaneously providing additional exothermic heat into the gasification column. This additional exothermic heat of reaction balances the overall endothermic character of the reaction, including the solid carbon and water gas transfer reactions, allowing for a nearly thermally neutral process, which allows for the injection of large amounts of oxygen and other Eliminates the need for expensive heat supply methods. The catalytic influence of carbon-alkali metal catalysts on gas phase reactions is different from reactions of carbon with steam, hydrogen or carbon dioxide or solid phase gas phase reactions; The reason is that it makes a substantial contribution to the existence of carbon atoms, and that it greatly reduces the endothermic nature of the overall reaction.

{1'Next 010 Crime 21C020C Ratio (Exothermic)'2) C
O+9 days 2 → days 200 CH4 (febrile) '3' C02
14 days 2 → 200 CH4 (pyrogenic) under appropriate conditions,
These reactions may be carried out within the gasification zone, and may be provided with large quantities of methane and additional exothermic heat which must be provided by oxygen injection or other means. Laboratory tests and pilot plant tests have shown that the raw product gas thus produced is present in equilibrium concentrations at the reaction conditions and consists primarily of hydrogen, carbon monoxide, carbon dioxide, methane and steam. The raw product gas is treated to remove steam and acid gases, mainly carbon dioxide and hydrogen sulfide, and the methane in the treated gas is reduced to an equilibrium concentration of carbon monoxide and hydrogen in the raw material gas. low-temperature separation of carbon monoxide and hydrogen in large quantities, and then drawing out methane as a high Btu gas;
Then, a method was proposed for producing high TU gas products using a steam gasification process in the presence of a carbon-alkali metal catalyst by returning carbon monoxide and hydrogen to the gasification tower. The presence of a carbon-alkali metal catalyst and an equilibrium amount of circulating carbon monoxide and hydrogen in the gasification column suppresses reactions that produce additional hydrogen and carbon dioxide, allowing nearly thermally neutral reactions to occur and essentially methane and carbon dioxide are produced. Since the overall reaction is nearly thermally neutral, only a small amount of heat input is required to preheat the carbonaceous feed and to maintain the reaction temperature of the reactants by compensating for heat losses from the gasification column. Bye. This small amount of heat can be provided by subheating the gaseous reactants in a conventional subheating furnace. The process described above enables the production of high Btu products from carbonaceous feedstock without separate conversion (shift) and methanation steps, thereby allowing pipeline-grade gas to be produced from coal and other carbon-purchasing materials. Although it significantly reduces the cost of manufacturing, it consumes a lot of energy because it uses relatively expensive steps of low-temperature separation and co-heating. Therefore, if production of high Btu pipeline grade gas is not required, a thermally neutral gasification process that does not utilize low temperature separation and subthermal steps may be used to combine a carbon-alkali metal catalyst with additional hydrogen and monoxide. It is desirable to gasify the carbonaceous material in the presence of carbon. It is therefore an object of the present invention to produce an intermediate intermediate by reacting coal, petroleum coke, heavy oil and other carbonaceous feedstocks with steam in the presence of a carbon-alkali metal catalyst and added hydrogen and carbon monoxide. A nearly thermally neutral method of producing Btu gas with a relatively low initial capital investment, inexpensive to operate, and more efficient than conventional production of gasified fuels from carbonaceous materials or coal. It is about providing.

According to the present invention, the intermediate Btu gas is prepared by: (1) converting steam to about 10,000F in the presence of a carbon-alkali metal catalyst and substantially equilibrium amounts of added hydrogen and carbon monoxide;
- at a temperature of about 15,000F (53,800 - 81,600), greater than about 10 sia (7.0X9/ground), preferably about 300 - about 150 + sja (21.1 - 105.5K)
react with carbon material under a pressure of ) withdrawing this raw material product gas from the reaction zone and treating it to remove acid gas and producing a treated gas; (m) withdrawing a portion of this treated gas as an intermediate Btu product gas; and (W) treating the remainder. (V) reacting the finished gas with steam in a steam reforming zone under conditions such that methane in the gas reacts with the steam to produce additional amounts of carbon monoxide and hydrogen; It has been found that this can be generated by a method consisting of sending the effluent stream from the castle to the reaction zone castle.

The amount of treated gas stream sent to the reforming zone is determined in part by the methane content of the treated gas. Typically, sufficient methane is present in this stream to produce carbon monoxide and hydrogen in sufficient quantities in the political zone, thereby producing intermediate Bt
u should compensate for the amount of these gases in the processed gas withdrawn as product gas. Therefore, the reforming zone effluent stream typically contains carbon monoxide and hydrogen in amounts equivalent to the equilibrium amounts of these gases present in the feed product gas, and thus mainly contains methane and carbon dioxide formation. Substantially equilibrium amounts of hydrogen and carbon monoxide are provided along with the carbon-alkali metal catalyst and steam to carry out the thermally neutral reaction. A sufficient amount of steam is usually mixed with the treated gas to be fed to the reforming zone.
A sufficient amount of unreacted steam is ensured to be present in the steam reforming zone, thus providing substantially all the steam necessary for the reactions taking place in the reforming zone.

The effluent stream from the porosity can also be used to heat the carbonaceous feed to reaction temperature and provide the sensible heat necessary to compensate for heat losses from the reaction swath. This means that the effluent is about 1000F - about 2500F higher than the temperature of the reaction zone.
This is achieved by operating the reforming zone at a temperature of (37.8 - 12 loo) and passing the effluent stream to the reaction zone without substantial cooling. The method of the present invention is a method for converting carbonaceous materials into gasified fuels at a lower cost and with greater energy efficiency than previously utilized or proposed methods.

The process involves reacting steam with carbon in the presence of a carbon-alkali metal catalyst and substantially equilibrium amounts of additional hydrogen and carbon monoxide to produce a substantially thermally neutral reaction, thereby creating a substantially thermally neutral reaction within the reaction zone. Mainly methane and carbon dioxide are formed. Unlike similar methods proposed previously,
The process produces an intermediate Btu gas that has wide application as an industrial fuel gas without the need for expensive and energy-consuming low-temperature separation steps and subthermal steps. The invention will now be explained in conjunction with the drawings.

The drawing is a flow diagram illustrating the process of the present invention for producing intermediate Btu gas by gasifying coal or similar carbonaceous solids with steam in the presence of a carbon-alkali metal catalyst and equilibrium amounts of hydrogen and carbon monoxide. It is. The process illustrated is to feed bituminous coal, subbituminous coal, lignite, coal char, coke or similar carbonaceous solids at elevated temperatures and to the feed solids with a solution of an alkali metal compound or a solution of a mixture of these compounds. After impregnation, these solids are gasified by reaction with steam in the presence of a carbon-alkali metal catalyst heated to a temperature sufficient to cause interaction between the alkali metal and the carbon present. One way to do this is shown below.

Solid feed materials ground to approximately 8 mesh or less on U.S. standard sieves must be placed in a feed conditioning plant or storage facility (
(not shown) to the conduit 10. The solids fed to line 10 are passed to a hopper 11 or similar container and from there via line 12 to feed preparation zone 14. This zone 14 is equipped with a screw conveyor or similar device 15 driven by a motor 16, a spray nozzle or similar device 17 for the alkali metal-containing solution supplied from a line 18, and a steam conveyor into this zone. a similar nozzle or equivalent means 19 for The steam supplied from pipe 20 serves to heat the impregnated solids and to create moisture. Steam is routed from the belt 14 via line 21 to a condenser, not shown above, from which it can be recovered for use as make-up water or for other purposes. The majority of the alkali metal-containing solution is circulated through a pipe 49 from an alkali metal recovery section, which will be described later. The necessary replenishment alkali metal solution can be introduced into line 18 through line 13. It is desirable to introduce sufficient alkali metal-containing solution into preparation zone 14 to provide about 1-5 weight percent of an alkali metal compound or mixture of such compounds to the coal or other carbonaceous solids.

About 5-30% is generally considered suitable. The dry impregnated solid particles prepared in zone 14 are drawn off in line 24 to a closed hopper or similar vessel 25 from where they are transferred to a star wheel feeder or equivalent means in line 27. 26, sufficient to entrain those solid particles into the stream of circulating product gas, steam, inert gas, or other high pressure carrier gas introduced from line 28 into line 29. Released under pressure. The carrier gas and its entrained solids are fed from line 29 to a manifold 30, then to a feed line 31, and then to a gasification column 32 via a nozzle (not shown). In place of, or in addition to, the hopper 25 and star wheel feeder 26, the feed system includes a parallel lock hopper,
Pressurized hopper, aerated feed tower (a
(erated pipes) or other devices for pressurizing the input feed solids stream to the desired pressure level may be used. The gasification tower 32 is about 300-150
It is generally desirable to operate at a pressure of 0 psia.

The carrier gas and entrained solids are introduced at a pressure slightly above the operating pressure of the gasification column. The carrier gas is about 3
It can be preheated to a temperature above 000F (149o0) but below the initial softening point of the coal or other feed material used. The feed particles are mixed with 1 pound (lk) of carrier gas.
Approximately 0.2-0.5 pounds (k9) of solid feed particles per 9)
) suspended in the carrier gas to a concentration of
end). The optimum ratio for a particular system depends in part on particle size, particle density, molecular weight of the gas used, temperature of the solid feed particles, temperature of the input gas stream, amount of alkali metal compound used, and other factors. Generally about 0.5-4 per pound (lk9) of carrier gas
．． A ratio of 0 pounds (k9) of solid feed particles is preferred. Gasification column 32 includes a fluidized bed of carbonaceous solids extending above an internal grate or inorganic distribution device, not shown.

The fluidized bed is maintained in a fluidized state by steam, hydrogen and carbon monoxide introduced through line 33, manifold 30, circularly spaced tubes and nozzles 35, and bottom inlet tube 36. The particular injection device shown is not critical; other injection methods for steam, hydrogen, and carbon monoxide may also be used. For example, in some cases it may be preferable to introduce these gases through multiple nozzles to achieve a more uniform distribution of the injected fluid and eliminate the possibility of channeling and associated problems. The space velocity of the rising gas in the fluidized bed is typically about 15-30 centimeters (steam, hydrogen and carbon monoxide)/1 centimeter (fluidized solids). Within the fluidized bed of gasification column 32, carbonaceous solids impregnated with an alkali metal compound or a mixture of such compounds are present at a temperature of about 1000-15000F (538-81600).
more preferably about 1200-14000
Processed at temperatures ranging from 649-761°C. At this temperature, the alkali metal component interacts with the carbon in the carbonaceous solids to form a carbon-alkali metal catalyst.
This catalyst equilibrates the gas phase reactions occurring during the gasification period under suitable reaction conditions to produce additional methane while simultaneously providing a sufficient amount of additional exothermic heat in situ.
Due to the gas phase equilibrium conditions formed as a result of the presence of the carbon-alkali metal catalyst, and because equilibrium amounts of hydrogen and carbon monoxide are injected with the steam near the bottom of the bed, the reaction products are normal. Consists primarily of methane and carbon dioxide. In the absence of the present catalyst and hydrogen and carbon monoxide, competing reactions that would normally tend to produce excess hydrogen and carbon monoxide are suppressed. At the same time, a substantial amount of exothermic heat is released as a result of the reaction of hydrogen with carbon oxides and the reaction of carbon monoxide with steam. This exothermic heat of reaction tends to balance the endothermic heat consumed in the steam and carbon reaction, thereby producing a thermally neutral reaction.
As far as the heat of reaction is concerned, the gasification column is thus broadly thermally balanced. The heat used to preheat the feed coal to reaction temperature and to compensate for heat losses from the gasifier is provided mostly by the excess heat in the steam, hydrogen and carbon monoxide. Without the exothermic heat provided by the catalytic gas phase reaction, the steam, hydrogen and carbon monoxide would have to be heated to temperatures well above those used in this invention. The carbon-alkali metal catalyst utilized in the process described above involves impregnating a carbonaceous feed with an alkali metal-containing solution and then converting the impregnated solids to approximately 8000 F (427 qo) in the gasification tower itself.
It is prepared by heating to above temperature.

It should be understood that the alkali metal catalysts used in the process of the present invention may be prepared without impregnation of the carbonaceous material or solids to be gasified or heating within the gasification column. For example, the heating step can be performed in the solids feed preparation zone or in an external heater. The carbonaceous solids used are most often those intended to be gasified, but in some cases carbonaceous materials other than feed solids may be used. In some cases, inert carriers with carbon attached to their outer surfaces include silica, alumina, silica-alumina, zeolites, and the like. The catalyst particles may consist essentially of carbon and alkali metals, or they may consist of carbon and alkali metals attached to an inert carrier, and the particles range from fine powders to phase agglomerates. It can be as large as . Approximately 4-100 mesh (
US Standard Sieve) particles are generally preferred. The dimensions used for a particular reaction operation will depend in part on gas velocities and other conditions within the system in which the catalyst is used. In fluidized bed systems, particle size depends in part on the operating conditions of the fluidized bed. In fixed bed or moving bed systems, the particle size of the catalyst is generally less important. A variety of alkali metal components can be used to prepare carbon-alkali metal catalysts.

Suitable alkali metal components include the alkali metals themselves, alkali metal carbonates, bicarbonates, formates, biphosphates, oxalates, aluminates, amides, hydroxides, acetates, sulfates ( alkali metal compounds such as sulfuric acid, hydrosulfate, sulfides, sulfuric acid salts, mixtures thereof, and other similar compounds. Since they are not all equally effective, it can be expected that catalysts prepared from particular alkali metal components will give better results under some conditions than others. Generally, cesium, potassium, sodium and lithium salts and alkali metal hydroxides derived from organic or inorganic acids with ionization constants of about 1 x 10-3 or less are preferred. Cesium compounds are the most effective, followed by potassium, sodium, and lithium compounds in that order. Among these compounds, potassium compounds, sodium compounds, and mixtures thereof are widely used because they have high activity and are cheaper than cesium compounds. Particularly effective are potassium carbonate and mixtures of potassium carbonate and sodium carbonate.
In the illustrated embodiment, the alkali metal component and the carbonaceous solid are prepared by dissolving a water-soluble alkali metal compound in an aqueous medium and impregnating particles of the carbonaceous solid with the resulting aqueous solution by impregnation or spraying. , and then combined to form an intimate mixture by drying.

It should be noted that other methods may be used to form such intimate mixtures. For example, in some cases, impregnation of carbonaceous materials involves suspending finely divided alkali metals or alkali metal compounds in a hydrocarbon solvent or other low viscosity, highly volatile inert solvent and then adding carbonaceous solids to the material. This can be carried out by treatment with this suspension solvent. In other cases, it may be advantageous to form a very finely divided alkali metal or alkali metal compound into a pellet with carbon in an oil or similar binder and then heat the pellet to a high temperature. There is. Furthermore, a method in which a fine carbonaceous material is simply mixed with a powdered alkali metal salt and then heated to a desired temperature, or any other method may be used in some cases. The mechanism of interaction that occurs when carbonaceous solids and alkali metal components are combined and then heated to elevated temperatures is not completely understood.

One possible explanation is that the alkali metal appears to react with the carbon to form a layered, intricate carbon-alkali metal compound and rust body.

Studies have shown that carbonaceous solids or alkali metal components alone are not sufficient to create equilibrium for gas phase reactions involving steam, hydrogen, carbon monoxide, carbon dioxide, and methane, and that catalytic activity is limited between carbon and alkali metals. was found to be obtained only when the compound or chain is present in the system. Therefore, both components must coexist in the catalyst. Experiments have shown that the catalyst resists degradation in the presence of sulfur compounds, is resistant to condensation at high temperatures, and equilibrates gas-phase reactions involving gases normally produced during coal gasification. I understand. As a result of these advantageous properties and others, the present catalyst has significant advantages over other catalysts previously used. Referring again to the drawings, the gasification tower 32
The gas leaving the fluidized bed is directed to the top of the tower, which acts as a separator, where particles that are too heavy for the gas leaving the bed to be entrained are returned to the bed.

If desired, the separator may include one or more cyclone separators or similar means to separate relatively large particles from the gas. Pipe line 37 from the top of the gasification tower
The gas drawn off contains an equilibrium mixture of methane, carbon dioxide, hydrogen, carbon monoxide and unreacted steam at reaction temperature and pressure. This gas also contains hydrogen sulfide,
Includes ammonia, other contaminants formed from sulfur and nitrogen contained in the feed, and entrained fines.
This feed product gas is introduced into a cyclone separator or similar device 38 for removal of large particles. The overhead gas is then directed via line 39 to a second separator 41 for small particle removal. The solids-free gas is withdrawn from the top of separator 41 into line 42, and the fines are returned to the gasification column or sent to an alkali metal recovery section. In the illustrated system, char particles having a high ash content are transferred from gasifier 32 to line 4
4, which controls the ash content in the system and also allows recovery and recycling of the alkali metal component of the catalyst. The solids in conduit 44 are separated from the conduit (diple
g) It is combined with the powder at the top of the gasification tower recovered through 40, 43, and 45, and then sent to the alkali metal recovery device 46. The recovery device 46 is typically a multi-stage countercurrent leaching device in which the high ash particles are countercurrently contacted with water, dilute formic acid solution, etc. introduced through a line 47. An aqueous solution of an alkali metal compound is passed from an alkali metal recovery device 46 to a pipe 48.
It is removed through lines 49 and 18 and recycled to feed preparation belt 14. The remaining ash, from which substantially all of the soluble alkali metal compounds have been leached, is withdrawn from recovery device 46 to line 50 for further processing to recover additional alkali metal components. Gas leaving the separator 41 is passed through line 42 to an air-to-air heat exchanger 51;
There, the gas is indirectly heat exchanged with the intermediate B gas which is recycled through line 72.

The cooled gas then passes through line 53 to waste heat boiler 5
4, where the gas is cooled by indirect heat exchange with water introduced through line 55. Sufficient heat is transferred from the gas to the water to convert the water to steam, which is then withdrawn into line 56. During this cooling step, unreacted steam in the gas from heat exchanger 51 is condensed and drawn off as condensate into line 57.
Cooled gas leaving waste heat boiler 54 in line 58 is sent to water scrubber 59. The gas stream rises through the scrubber and is contacted by water injected from line 60 at the top of the scrubber. The water absorbs some of the ammonia and hydrogen sulfide in the gas stream and is then withdrawn from the bottom of the scrubber into line 61 and then sent to downstream equipment for after-treatment. The water-scrubbed gas stream is withdrawn from the scrubber to line 62 in preparation for subsequent processing to remove most of the hydrogen sulfide and other acid gases. The gas stream is passed from the water scrubber 59 via line 62 to the bottom of the solvent scrubber 63.

Here the gases rise through the contacting zone of the scrubber 63 and contain monoethanolamine, jetanolamine, sodium salt solutions of amino acids, methanol, hot potassium carbonate, and other solvents which are introduced from line 64 into the top of the solvent scrubber. come into contact with the downdraft. If desired, the solvent scrubber can be equipped with spray nozzles, perforated plates, bubble cap plates, fillers, or other means to promote gas and solvent contact. As the gas rises through the contacting zone, hydrogen sulfide, carbon dioxide, and other acid gases are absorbed by the solvent and exit line 65. Spent solvent containing carbon dioxide, hydrogen sulfide, and other contaminants is conducted from this line 65 to a stripper, not shown.
It is then contacted with steam or other stripping gas to force out the absorbed contaminants and thereby regenerate the solvent. The regenerated solvent then passes through line 64 to scrubber 6.
It can be returned to the top of 3 and sprayed. Mainly methane, hydrogen and carbon monoxide are transported from the gasification tower 32 to the pipe 3.
Clean gas containing an amount equivalent to the equilibrium amount of these gases in the raw material product gas drawn out to 7 is drawn out from the top of the solvent scrubber 63 to a conduit 66. In some cases, it may be desirable to operate the solvent scrubber under conditions such that some carbon dioxide is present in the top gas stream. The methane content in this top gas is typically in the range of about 20-60 mole percent, and the gas has an intermediate Btu heating value, typically about 400-75 tu/ft3 (11.3 -21.$tu/). A part of this gas is recovered from pipe 75 as Nakakoriyama product gas,
This can then be used as a fuel for heat sources in other industrial plants or for other uses. The portion of the gas that is not recovered as product is sent through line 67 to compressor 68 where the gas pressure is approximately 25-75 psi below the operating pressure in gasifier 32. 5
．． 27k9'). The pressurized gas is passed from the compressor 68 through a pipe 69 to a steam reforming furnace 71.
Seven tubes are passed through the flue. Here, this pressurized gas absorbs heat in indirect heat exchange with the hot flue gas generated in the furnace 71. This gas is tube 70
It exits into line 72 and is combined with steam generated in waste heat boiler 54 and injected into line 72 via line 56 . This mixture of intermediate B gas and steam is then passed through line 72 to air-air heat exchanger 51.
There, it is heated by indirectly exchanging heat with the raw material generated gas from the separator 41. The heated mixture is removed from heat exchanger 51 and passed through line 73 and then into steam reforming furnace 71. The preheated steam-intermediate Bm gas mixture (in line 73) typically consists primarily of carbon monoxide, hydrogen, steam and methane.

The mixture is then introduced into the inner tube 74 of the steam reforming furnace 71 where an interaction takes place between the intermediate B gas and the steam in the presence of a conventional steam reforming catalyst.
The catalyst is usually a metal component supported on an inert carrier. This metal component is typically selected from the W-B and iron groups of the periodic table, including chromium, molybdenum, tungsten, nickel, iron, and cobalt. Small amounts of calcium carbonate or similar compounds may also be included as accelerators. Suitable inert carriers are silica, alumina, silica alumina, zeolites, and the like. The illustrated steam reforming furnace is shown as being equipped with a tube 70 that heats the high-pressure intermediate B gas drawn out from the compressor 68 into the pipe line 69. Steam teaching furnace 7
1 is the methane in the middle B melon gas on the wedding day 200 CH4 one crime 2
It is operated under such conditions that it produces additional hydrogen and carbon monoxide according to the amount of CO.

The temperature inside the reforming furnace 71 is usually about 1200-18000F.
(649-98 years old), preferably maintained at a value about 100-2500F (55-130q0) higher than the temperature of the gasification tower 32. The pressure is about 10-3 higher than that of the gasification tower.
Snake si (0.7-2.1k9/c fin) is kept high. The ratio of steam to intermediate Btu gas is approximately 2.0-4
．． 0 or more, preferably about 2.5-3.5. The reformer is preferably heated by a portion of the intermediate Btu gas removed as product from line 75. The required amount of gas is drawn from line 75 to line 76 and then to the steam reformer 7.
It is directly fed into the firebox inside the firebox. The effluent stream from the steam furnace 71 (usually a mixture consisting primarily of hydrogen, carbon monoxide, and unreacted steam) is passed to the gasification column 32 via lines 77, 76, and 33; It is desirable to avoid substantial cooling.

This steam is the primary source of hydrogen, carbon monoxide and steam required in the gasification column, in addition to the carbon-alkali metal catalyst, producing a thermally neutral gas consisting primarily of carbon dioxide and methane. Let the reaction take place. Therefore, the reforming furnace 71
The effluent stream supplies sufficient of these gases to provide the substantially equilibrium amounts of carbon monoxide and hydrogen required in the gasification column and substantially all of the steam required for the reactions carried out in the gasification column. It is desirable to contain sufficient reaction steam for the reaction. To achieve the required amount of hydrogen and carbon monoxide in the effluent stream, sufficient methane must be present in the feed stream to the reformer so that sufficient carbon monoxide and hydrogen are produced by the steam reforming of the methane. This should compensate for the amount of hydrogen and carbon monoxide removed in the intermediate Btu product gas withdrawn from line 75. This can be achieved by adjusting the magnitude of the gas flow supplied to the reformer from the point of line 67, and thus the methane content. If the amount of steam added to the reformer feed stream in line 72 via line 56 does not substantially exceed the amount consumed in the furnace and the required amount is added to the reformer effluent stream, Additional steam can be blown into line 72 from line 78 if it contains unreacted steam. From the standpoint of thermal efficiency, it is desirable to use the steam reforming step in the present invention in a manner that eliminates the need for a separate preheating step. This makes the burning rate of the waste furnace approximately 100 - 2
By preheating the carbonaceous feed to the reaction temperature by adjusting the temperature to 500 F (55 - 130 oo) higher and maintaining all reactants at that temperature to compensate for heat loss lost during gasification. It can be achieved. In this regard, it is important that the effluent from the steam reformer be sent to the gasification tower with virtually no cooling occurring. SUMMARY OF THE INVENTION Accordingly, the present invention provides an improved method for gasifying carbonaceous materials with steam in the presence of a carbon-alkali metal catalyst and substantially equilibrium amounts of additional hydrogen and carbon monoxide; It will be apparent that it is relatively simple, energy efficient, and less expensive than previously proposed.

[Brief explanation of the drawing]

The drawing is a flow sheet illustrating a method of carrying out the invention. The main members in the figure are as follows. 11: Hopper, 1
4: Feed preparation zone, 15: Screw conveyor, 17
, 19: spray nozzle, 25: hopper, 26: feeding device, 30: manifold, 31: supply pipe, 32: gasification tower, 35: nozzle, 36: bottom inlet pipe, 41: separator,
46: Alkali metal recovery device, 51: Air-air heat exchanger,
54: Waste heat boiler, 59: Water scrubber, 63: Solvent scrubber, 71: Steam reforming furnace.

Claims (1)

Claims: 1. A method of producing an intermediate Btu product gas from a carbonaceous feedstock and steam, comprising: (a) directing the steam to about 1000-1500°F (538-8°F) in a reaction zone;
reaction temperature of 16 °C) and 100 psia (7.0, kg
/cm^2), a carbon-alkali metal catalyst and sufficient additional hydrogen and carbon monoxide in the reaction zone to provide substantially equilibrium amounts of hydrogen and carbon monoxide at the reaction temperature and pressure. (b) producing a feedstock from the reaction zone containing substantially equilibrium amounts of methane, carbon dioxide, steam, hydrogen and carbon monoxide at the reaction temperature and pressure; (c) treating the raw material product gas to remove acid gas; and (d) transferring a portion of the thus treated gas to intermediate B.
(e) contacting the remaining treated gas with steam in a steam reforming zone under conditions such that methane in the treated gas reacts with the steam to produce additional hydrogen and carbon monoxide; and (f) directing an effluent stream containing primarily hydrogen, carbon monoxide, and unreacted steam from the steam reforming zone to the reaction zone to eliminate the additional hydrogen needed in the reaction zone. and carbon monoxide. 2. The intermediate Btu of claim 1, wherein the carbon-alkali metal catalyst is prepared by treating the carbonaceous feedstock with an alkali metal compound and then heating it to the reaction temperature in the pre-reaction zone.
Method of producing product gas. 3. The intermediate Btu product of claim 1, wherein at least a portion of the carbonaceous feedstock is impregnated with an aqueous solution of a potassium compound and introduced into the dried upper reaction zone to form a carbon-alkali metal catalyst. Gas production method. 4. A method for producing an intermediate Btu product gas as claimed in claim 3, wherein the aqueous solution of potassium compounds is recovered from carbon drawn from the reaction zone. 5 Claims 1 to 5 in which the carbonaceous feed material is coal
4. A method for producing an intermediate Btu product gas according to any one of Item 4. 6 The heat content of the intermediate Btu product gas is approximately 400-750B
A method for producing an intermediate Btu product gas according to any one of claims 1 to 5, wherein the intermediate Btu product gas is tu/f^3 (11.3-21.2 Btu/m^3). 7 Reaction temperature is about 1200-
7. A method of producing an intermediate Btu product gas according to any of claims 1-6, wherein the temperature is 1400<0>F (649-760[deg.]C). 8 The reaction pressure is approximately 300-1500 psia (21.1
-105.5 kg/cm^2) The method for producing an intermediate Btu product gas according to any one of claims 1 to 7. 9 The treated gas contacted with steam in the steam reforming zone contains sufficient methane to produce sufficient additional hydrogen and carbon monoxide in the reforming zone so that the effluent from the reforming zone containing sufficient amounts of carbon monoxide and hydrogen to provide an equilibrium amount of these gases in the reaction zone;
Intermediate Bt according to any one of claims 1 to 8
u Manufacture of product gas. 10 A sufficient amount of steam is contacted with the treated gas in a steam reforming zone such that the effluent from the reforming zone contains sufficient unreacted steam to provide substantially all of the steam required in the reaction zone. A method for producing an intermediate Btu product gas according to any one of claims 1 to 9, comprising: 11. A steam reforming zone wherein the heat content of the effluent from said reforming zone is sufficient to provide substantially all of the sensible heat required to preheat the carbonaceous feed to reaction temperature. A method for producing an intermediate Btu product gas according to any one of items 1 to 10. 12. Claims 1-11 wherein the effluent from the steam reforming zone is sent to the reaction zone substantially uncooled.
A method for producing an intermediate Btu product gas according to any one of paragraphs.